During the screening for inhibitors of nitric oxide production in LPS-activated macrophage, RAW 264.7 cells, two coumarins were isolated from chloroform extract of the root of Polygonum cuspidatum. They were identified as decursin (1) and decursinol angelate (2) on the basis of spectroscopic methods. The $IC_{50}$ values of these compounds on NO production were $0.76;{mu}M$ (1) and $2.6;{mu}M$ (2), respectively. However, the iNOS activity was not inhibited by treatment with these compounds. Their inhibitory effect on NO production seems to result from the suppression of iNOS induction through the suppression of NF-kB activity.